/*****************************************************************************
 * kconfig_define.c
 *
 * Copyright (C) 2019 wanshijie wanshijie@126.com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 ****************************************************************************/

/*****************************************************************************
 * Included Files
 ****************************************************************************/

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>

/*****************************************************************************
 * Trace Definitions
 ****************************************************************************/

/*****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define LINESIZE (PATH_MAX > 256 ? PATH_MAX : 256)

/*****************************************************************************
 * Private Types
 ****************************************************************************/

/*****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/*****************************************************************************
 * Private Data
 ****************************************************************************/

static char line[LINESIZE + 1];

/* These are configuration variable name that are quoted by configuration tool
 * but which must be unquoted when used in C code.
 */
static const char *dequote_list[] = {
    NULL /* Marks the end of the list */
};

/*****************************************************************************
 * Public Data
 ****************************************************************************/

/*****************************************************************************
 * Private Functions
 ****************************************************************************/

/* Skip over any spaces */

static char *skip_space(char *ptr)
{
    while (*ptr && isspace((int)*ptr))
        ptr++;
    return ptr;
}

/* Find the end of a variable string */

static char *find_name_end(char *ptr)
{
    while (*ptr && (isalnum((int)*ptr) || *ptr == '_'))
        ptr++;
    return ptr;
}

/* Find the end of a value string */

static char *find_value_end(char *ptr)
{
    while (*ptr && !isspace((int)*ptr)) {
        if (*ptr == '"') {
            do
                ptr++;
            while (*ptr && *ptr != '"');
            if (*ptr)
                ptr++;
        } else {
            do
                ptr++;
            while (*ptr && !isspace((int)*ptr) && *ptr != '"');
        }
    }
    return ptr;
}

/* Read the next line from the configuration file */

static char *read_line(FILE *stream)
{
    char *ptr;

    for (;;) {
        line[LINESIZE] = '\0';
        if (!fgets(line, LINESIZE, stream)) {
            return NULL;
        } else {
            ptr = skip_space(line);
            if (*ptr && *ptr != '#' && *ptr != '\n') {
                return ptr;
            }
        }
    }
}

/* Parse the line from the configuration file into a variable name
 * string and a value string.
 */

static void parse_line(char *ptr, char **varname, char **varval)
{
    /* Skip over any leading spaces */

    ptr = skip_space(ptr);

    /* The first no-space is the beginning of the variable name */

    *varname = skip_space(ptr);
    *varval  = NULL;

    /* Parse to the end of the variable name */

    ptr = find_name_end(ptr);

    /* An equal sign is expected next, perhaps after some white space */

    if (*ptr && *ptr != '=') {
        /* Some else follows the variable name.  Terminate the variable
       * name and skip over any spaces.
       */

        *ptr = '\0';
        ptr  = skip_space(ptr + 1);
    }

    /* Verify that the equal sign is present */

    if (*ptr == '=') {
        /* Make sure that the variable name is terminated (this was already
       * done if the name was followed by white space.
       */

        *ptr = '\0';

        /* The variable value should follow =, perhaps separated by some
       * white space.
       */

        ptr = skip_space(ptr + 1);
        if (*ptr) {
            /* Yes.. a variable follows.  Save the pointer to the start
           * of the variable string.
           */

            *varval = ptr;

            /* Find the end of the variable string and make sure that it
           * is terminated.
           */

            ptr  = find_value_end(ptr);
            *ptr = '\0';
        }
    }
}

static char *dequote_value(const char *varname, char *varval)
{
    const char **dqnam;
    char *       dqval = varval;
    char *       ptr;
    int          len;
    int          i;

    if (dqval) {
        /* Check if the variable name is in the list of strings to be dequoated */

        for (dqnam = dequote_list; *dqnam; dqnam++) {
            if (strcmp(*dqnam, varname) == 0) {
                break;
            }
        }

        /* Did we find the variable name in the list of configuration variables
       * to be dequoted?
       */

        if (*dqnam) {
            /* Yes... Check if there is a trailing quote */

            len = strlen(dqval);
            if (dqval[len - 1] == '"') {
                /* Yes... replace it with a terminator */

                dqval[len - 1] = '\0';
                len--;
            }

            /* Is there a leading quote? */

            if (dqval[0] == '"') {
                /* Yes.. skip over the leading quote */

                dqval++;
                len--;
            }

            /* A special case is a quoted list of quoted strings.  In that case
            * we will need to remove the backspaces from the internally quoted
            * strings.  NOTE: this will not handle nested quoted quotes.
            */

            for (ptr = dqval; *ptr; ptr++) {
                /* Check for a quoted quote */

                if (ptr[0] == '\\' && ptr[1] == '"') {
                    /* Delete the backslash by moving the rest of the string */

                    for (i = 0; ptr[i]; i++) {
                        ptr[i] = ptr[i + 1];
                    }

                    len--;
                }
            }

            /* Handle the case where nothing is left after dequoting */

            if (len <= 0) {
                dqval = NULL;
            }
        }
    }

    return dqval;
}

static void generate_definitions(FILE *stream)
{
    char *varname;
    char *varval;
    char *ptr;

    /* Loop until the entire file has been parsed. */

    do {
        /* Read the next line from the file */

        ptr = read_line(stream);
        if (ptr) {
            /* Parse the line into a variable and a value field */

            parse_line(ptr, &varname, &varval);

            /* Was a variable name found? */

            if (varname) {
                /* Yes.. dequote the value if necessary */

                varval = dequote_value(varname, varval);

                /* If no value was provided or if the special value 'n' was provided,
               * then undefine the configuration variable.
               */

                if (!varval || strcmp(varval, "n") == 0) {
                    printf("#undef %s\n", varname);
                }

                /* Simply define the configuration variable if it has the special
               * value "y"
               */

                else if (strcmp(varval, "y") == 0) {
                    printf("#define %s 1\n", varname);
                }

                /* Otherwise, use the value as provided */

                else {
                    printf("#define %s %s\n", varname, varval);
                }
            }
        }
    } while (ptr);
}

static void show_usage(const char *progname)
{
    fprintf(stderr, "USAGE: %s <abspath of .config>\n", progname);
    exit(1);
}

/*****************************************************************************
 * Public Functions
 ****************************************************************************/

int main(int argc, char **argv, char **envp)
{
    FILE *stream;

    if (argc != 2) {
        fprintf(stderr, "Unexpected number of arguments\n");
        show_usage(argv[0]);
    }

    stream = fopen(argv[1], "r");
    if (!stream) {
        fprintf(stderr, "open %s failed: %s\n", argv[1], strerror(errno));
        exit(3);
    }

    printf("/* This configure code -- Autogenerated! Do not edit. */\n");
    printf("\n");
    printf("#ifndef __PLUM_CONFIG_H__\n");
    printf("#define __PLUM_CONFIG_H__\n\n");

    generate_definitions(stream);

    printf("\n");
    printf("#endif /* __PLUM_CONFIG_H__ */\n");
    fclose(stream);

    return 0;
}
/****************************************************************************/
/*                                                                          */
/*  End of file.                                                            */
/*                                                                          */
/****************************************************************************/
